The present invention relates to a contact plug that enables the electrical connection of a plug-in terminal and an electronic component. More particularly, the present invention relates to an electric contact plug for connecting a type of tip jack input device to an external electronic circuit.
This type of electric contact plug is frequently used in application environments that are exposed to relatively high vibration levels, as, for example, in a motor vehicle. Since the connection principle for this type of electric contact plug is based on a clamping effect between the electric contact plug and the input device, relative movement may occur between the electric contact plug and the input device, depending on the force of the vibrations. As a result, this relative movement can cause undesirable wear and/or corrosion of both the contact plug and the input device.
Therefore, it is desirable for an electric contact plug used in a motor vehicle to avoid the problems of friction wear and corrosion, and yet be simple and economical to manufacture. Furthermore, it is desirable to configure such an electric contact plug in a single unit, and it should also be compatible with thick-wire bonding techniques, which are becoming ever more popular in automotive technology.
A process and apparatus for a prior art type of connection device is disclosed in European patent documents EP 0 794 847 B1 and EP 0 649 701 A1, which are incorporated herein by reference. A miniature tip jack that is free of frictional corrosion is disclosed in EP 0 794 847 B1. This tip jack, however, is expensive to produce, because of its relatively complicated configuration, and its high cost. Moreover, this prior art tip jack cannot be used for thick-wire bonding.
Therefore, it is an object of the present invention to configure an electric contact plug that avoids the aforementioned friction and corrosion problems, that is compatible with thick-wire bonding applications, and that can be produced easily and economically.
This object is attained through an inventive embodiment of an electric contact plug, which receives a tip jack input at a first end, and routes this electrical connection to an electronic component, such as a printed circuit board, at a second end. The inventive electric contact plug comprises:
a) a plug-in zone at the first end, located within an L-shaped area of the electric contact plug, and having receiving tongues for receiving the tip jack,
b) a connection zone at the second end, having a bonding pad for connecting to the electronic component,
c) an intermediate zone, connected between the plug-in zone and the connection zone, wherein the intermediate zone comprises at least one form-changing area, having less resistance to form change than other areas of the intermediate zone, which enables the plug-in zone to move in a plug-in direction, as the intermediate zone is deformed.
Thus, when vibrations occur, as in a motor vehicle, the tip jack is held securely within the tongues of the plug-in zone, while the intermediate zone form-changing area(s) allow for movement to compensate for any vibrational stresses. As a result, deterioration of the plug-in zone is avoided by eliminating friction between the tip jack and the receiving tongues of the plug-in zone.
The expression xe2x80x9cresistance to form changesxe2x80x9d shall hereinafter designate a material characteristic that is essentially inversely proportional to the elasticity of the material.
The purpose of the essentially L-shaped form of the electric contact plug, as well as the location of the plug-in zone in this L-shaped area, is to achieve an especially compact structure. The expression xe2x80x9cL-shapedxe2x80x9d shall include in this context, not only an exact right angle between the legs of the L-shaped area, but also minor deviations from a right angle.
The inventive electric contact plug can be used to special advantage for the connection of electrical/mechanical components, such as pressure sensors and solenoid valves, to an electronic control system. In a preferred application of the invention, such electrical/mechanical components are installed in an electronic control apparatus, together with the electronic control system. Due to the deformability of the inventive electric contact plug, tolerances can be compensated for during the manufacture and assembly of the electronic control apparatus.
In an advantageous embodiment of the invention, the entire plug-in zone is located in one leg of an L-shaped area, while the other leg functions as a bending beam, as is known in the mechanical technology art.
The problems of frictional wear and frictional corrosion are avoided in the inventive electric contact plug, as a result of the deformability of the intermediate zone. This deformability allows a limited movement of the plug-in zone, relative to the connection zone, so that smaller movements of the PLUG IN connection, as might be caused by vibrations, are eliminated through the compensating action of the intermediate zone. To this end, at least one form-changing area, with a lower resistance to form change than other areas of the intermediate zone, is included within the intermediate zone. As a result, the deformation of the intermediate zone takes place at a defined location, in the manner of an articulation.
In an advantageous further development of the invention, a second form-changing area, with reduced resistance to form change, is also included within the intermediate zone. This is done so that the preferred form changes of both the first and second form-changing areas take place along parallel axes. The advantage over a single form-changing area is that pivoting of the plug-in zone, when subject to vibrations, can be more easily avoided. In addition, relative movement between the plug-in zone and the electric contact plug, at a right angle to the plug-in direction, can also be more easily avoided. Furthermore, frictional forces between the plug-in zone and the sides of a receiving device holding the electric contact plug can be avoided, or at least reduced.
In another advantageous development, the inventive electric contact plug may include multiple angles in the area of the connection zone, and/or the intermediate zone, preferably in the form of an S, or a meandering form. This type of configuration can result in an especially small and compact electric contact plug, which enables it to be used in electronic devices where space is at a premium.
In another advantageous development of the invention, the connection zone also serves as a mechanical attachment point for the electric contact plug, obviating the need for another special area of the electric contact plug to be used for this purpose. This feature enhances both the economic production and the compact configuration of the electric contact plug.
The first and/or second form-changing areas have, as previously described, a lower resistance to form change than the other areas of the intermediate zone. This increased elasticity can be achieved, e.g., by subjecting the form-changing areas to heating, while the cross-section of the material remains essentially unchanged. In accordance with another advantageous embodiment of the invention, a lower resistance to form change can also be achieved by reducing the cross-section of the material in the intermediate zone.
For this embodiment, it is especially advantageous to reduce the thickness of the material, because this results in a significant reduction of the geometrical moment of inertia for a comparatively minor reduction of the cross-section of the material. As such, the electrical resistance of the intermediate zone is increased minimally in the form-changing areas.
In another advantageous development of the invention, the plug-in zone has at least two receiving tongues to receive a tip jack, or similar input device. The exterior contour of the receiving tongues tapers in the direction away from the intermediate zone, when the input device is not plugged in. In comparison with prior art contact plugs, whose exterior contours of the plug-in zone are essentially parallel, this tapering feature of the inventive plug-in zone provides an increased clamping force between the receiving tongues and the input device, while the space requirement remains the same. As a result, subsequent frictional wear and corrosion in the plug-in zone can be avoided even more efficiently.
Another feature of the invention is that the cross-sectional surface in at least part of each receiving tongue changes in a linear fashion, preferably in the central area of the receiving tongue. Therefore, when the input device is plugged in, thus expanding the plug-in zone of the electric contact plug, the resulting mechanical stresses are distributed evenly, minimizing the possibility of excessive localized stress. As such, the material requirements, and corresponding weight of the contact plug, are reduced. This enhances the durability and reliability of the inventive electric contact plug.
It is advantageous to design the spring action of the receiving tongues so that the holding force against the input device is greater than, and preferably twice that, of the force required to overcome the resistance to form change of the form-changing areas, which enable deformation in the intermediate zone.
In accordance with another advantageous development, the connection zone of the electric contact plug has a bonding area, for making a connection to an electronic component. Thus, the inventive electric contact plug is fully compatible with applications requiring thick-wire bonding technology. Typically, electric contact plugs are made of copper-beryllium, or copper-tin material. These materials, however, are subject to oxidation, which is detrimental to the application of thick-wire bonding technology. In another advantageous development of the invention, therefore, the bonding area is provided, at least in part, with an aluminum coating. As such, the inventive electric contact plug can be used advantageously in thick-wire bonding applications, since an aluminum-oxide layer is not detrimental to bonding. It is also advantageous to employ laser cleaning of the bonding area immediately before bonding. Where this type of cleaning is used, it is possible to dispense with the aluminum coating.
In another advantageous development, the connection zone is coated galvanically in the bonding area. The preferred coating material for this application is nickel-phosphorus.
Another feature of the invention is that a receiving device is used to house the electric contact plug, with the connection zone held securely in place, relative to the receiving device. The electric contact plug can be assembled quite easily, and can be attached to an external electrical device by means of extrusion-coating the receiving device. In this configuration, the plug-in zone retains its mobility relative to the connection zone, since the connection zone is fixed relative to the electrical device, due to its immobile position in the receiving device.
It should be noted that an extrusion-coating finishing step is different from a casting finishing step, because the extrusion coating always results in a rigid attachment. In a casting finishing step, an elastic attachment is also possible, as for example, when using a permanently elastic casting mass.
In the assembly of a receiving device by the extrusion-coating method, it is desirable to use a relatively hard, or inflexible material, preferably hard plastic. It is also desirable to use a labyrinth seal to protect the interior of the receiving device from the extrusion-coating mass.
In a preferred embodiment of the receiving device, a mobility-limiting means is incorporated internally, which limits the mobility of the plug-in zone and/or the intermediate zone, relative to the receiving device. Through suitable sizing of this mobility-limiting means, the anticipated vibration stresses are absorbed adequately, which prevents the occurrence of large movements, or plastic deformation, of the electric contact plug.
Finally, another advantageous embodiment of the invention comprises a receiving device configured in two parts. This embodiment can take either of two forms:
a) where the separation plane 34 of the two parts is essentially perpendicular to the axis 19 of the preferred deformation direction of the first form-changing area, as shown in FIG. 7, and
b) where the separation plane 35 is essentially parallel to the axis 19 of the preferred deformation direction of the first form-changing area, as shown in FIG. 16.
Either configuration allows for the simple assembly of the electric contact plug within one part of the receiving device, with the other part enclosing the open side of the electric contact plug, and attaching to the first part in an interlocking fashion, thus completing the assembly of the electric contact plug within the receiving device. Due to the simplicity and ease of this type of assembly configuration, the manufacture of the inventive electric contact plug and receiving device can be fully automated, and implemented by machine.